Identification and characterization of HLA-A24 specific XBP1 CD138 (Syndecan-1) and CS1 (SLAMF7) peptides inducing antigens-specific memory cytotoxic T lymphocytes targeting multiple myeloma

摘要

XBP1 (X-box binding protein 1), CD138 (Syndecan-1), and CS1 (SLAMF7) are highly expressed antigens in cancers including multiple myeloma (MM). Here we identify and characterize immunogenic HLA-A24 peptides derived from these antigens for potential vaccination therapy of HLA-A24+ patients with MM. The identified immunogenic HLA-A24-specific XBP1 unspliced (UN)185-193 (I S P W I L A V L), XBP1 spliced (SP)223-231 (V Y P E G P S S L), CD138265-273 (I F A V C L V G F) and CS1240-248 (L F V L G L F L W) peptides induced antigen-specific CTL with anti-MM activity in an HLA-A24 restricted manner. Furthermore, a cocktail containing the four HLA-A24 peptides evoked MM-specific CTL with distinct phenotypic profiles (CD28, CD40L, 41BB, CD38, CD69) and anti-tumor activities, evidenced by perforin upregulation, CD107a degranulation (cytotoxicity) and Th1 type cytokines (IFN-γ/IL-2/TNF-α) production in response to HLA-A24⁺ MM cells. The multipeptide-specific CTL included antigen-specific memory CD8⁺ T cells expressing both T cell activation (CD38, CD69) and immune checkpoints antigens (CTLA, PD1, LAG3, TIM3). These results provide the framework for a multipeptide vaccination therapy to induce tumor-specific CTL in HLA-A24 positive patients with myeloma and other cancers expressing these antigens.